From 9cb11bdcac69471a3962397b75c3fdbb374d3962 Mon Sep 17 00:00:00 2001
From: arngo <27396817+arngo@users.noreply.github.com>
Date: Fri, 17 Dec 2021 22:13:15 -0500
Subject: implement alignment rule

---
 app/components/rules/alignment.rb |  2 ++
 app/main.rb                       |  2 ++
 app/systems/rules/alignment.rb    | 24 ++++++++++++++++++++++++
 app/tick.rb                       |  4 ++++
 4 files changed, 32 insertions(+)
 create mode 100644 app/components/rules/alignment.rb
 create mode 100644 app/systems/rules/alignment.rb

diff --git a/app/components/rules/alignment.rb b/app/components/rules/alignment.rb
new file mode 100644
index 0000000..a62cc78
--- /dev/null
+++ b/app/components/rules/alignment.rb
@@ -0,0 +1,2 @@
+FF::Cmp.new('BoidsAlignment',
+           strength: 10)
diff --git a/app/main.rb b/app/main.rb
index 1ab9e32..20cc937 100644
--- a/app/main.rb
+++ b/app/main.rb
@@ -6,6 +6,7 @@ require 'app/components/sprite.rb'
 require 'app/components/boid.rb'
 require 'app/components/rules/bounds.rb'
 require 'app/components/rules/cohesion.rb'
+require 'app/components/rules/alignment.rb'
 require 'app/components/debug/debug_vector_arrow.rb'
 
 require 'app/systems/render.rb'
@@ -13,6 +14,7 @@ require 'app/systems/update_boid_sprite.rb'
 require 'app/systems/update_boid_position.rb'
 require 'app/systems/rules/bounds.rb'
 require 'app/systems/rules/cohesion.rb'
+require 'app/systems/rules/alignment.rb'
 require 'app/systems/rules/reset_change_vector.rb'
 require 'app/systems/debug/debug_render_vector_arrow.rb'
 
diff --git a/app/systems/rules/alignment.rb b/app/systems/rules/alignment.rb
new file mode 100644
index 0000000..2c2af11
--- /dev/null
+++ b/app/systems/rules/alignment.rb
@@ -0,0 +1,24 @@
+FF::Scn::BoidRules.add(
+  FF::Sys.new('BoidsAlignment', priority: 50) do
+    group_velocity = [0.0, 0.0]
+    boids_count = FF::Cmp::BoidsCohesion.data.count
+
+    FF::Cmp::BoidsAlignment.each do |alignment|
+      boid = alignment.entities[0].components[FF::Cmp::Boid][0]
+      group_velocity[0] += boid.vx
+      group_velocity[1] += boid.vy
+    end
+
+    FF::Cmp::BoidsAlignment.each do |alignment|
+      boid_update = alignment.entities[0].components[FF::Cmp::Boid][0]
+      move_boid = group_velocity.dup
+      move_boid[0] -= boid_update.vx
+      move_boid[1] -= boid_update.vy
+      move_boid[0] /= boids_count - 1.0
+      move_boid[1] /= boids_count - 1.0
+
+      boid_update.cx += (move_boid[0] - boid_update.vx) / alignment.strength
+      boid_update.cy += (move_boid[1] - boid_update.vy) / alignment.strength
+    end
+  end
+)
diff --git a/app/tick.rb b/app/tick.rb
index 7c44f47..077c4bb 100644
--- a/app/tick.rb
+++ b/app/tick.rb
@@ -1,19 +1,23 @@
 FF::Ent.new(FF::Cmp::Sprite.new,
             FF::Cmp::Boid.new(x: 10, y: 10, vx: 0, vy: 0),
             FF::Cmp::BoidBounds.new,
+            FF::Cmp::BoidsAlignment.new,
             FF::Cmp::BoidsCohesion.new)
 FF::Ent.new(FF::Cmp::Sprite.new,
             FF::Cmp::Boid.new(x: 50, y: 50),
             FF::Cmp::BoidBounds.new,
+            FF::Cmp::BoidsAlignment.new,
             FF::Cmp::BoidsCohesion.new)
 FF::Ent.new(FF::Cmp::Sprite.new,
             FF::Cmp::Boid.new(x: 70, y: 20),
             FF::Cmp::BoidBounds.new,
+            FF::Cmp::BoidsAlignment.new,
             FF::Cmp::BoidsCohesion.new)
 FF::Ent.new(FF::Cmp::DebugVectorArrow.new(length: 5),
             FF::Cmp::Sprite.new,
             FF::Cmp::Boid.new(x: 150, y: 250),
             FF::Cmp::BoidBounds.new,
+            FF::Cmp::BoidsAlignment.new,
             FF::Cmp::BoidsCohesion.new)
 FF::Scn::Debug.add(FF::Sys::DebugRenderVectorArrow)
 @pause = false
-- 
cgit v1.2.3